Battery powered motor system for low power application

ABSTRACT

An article of motion such as a toy has moving parts that are motivated slowly and with low torque by an electronic timepiece movement.

The present invention relates to toys, playthings or premium products such as electronic desktop decorations that produce a relatively slow and low-torque movement.

BACKGROUND OF THE INVENTION

There are classes of product in which a slow motion is desired, for example to mimic life-like movements (the limb articulation or gestures of a doll, the opening and closing of eyelids, or human facial expressions). There exist numerous prior inventions that meet the challenge with heavily geared-down DC motors, complicated mechanical contraptions, electromagnets, air bags or combinations thereof, to produce such movements.

DC motors are widely employed in the toy industry to induce toy motions, as in battery operated toy cars or animated figures. While producing high rotational speed and high torque, DC motors suffer from high current drain, especially when obstructed or stalled. For example, U.S. Pat. No. 4,695,016 to S. Worack (1987) described a system that used a DC motor and gear train and complex mechanical structures to produce a relatively slow throw action implementing a model train rail switch. The motor disclosed in the above US patent had to be specially designed for low stall current, to minimise battery drain when the throw-switch action was obstructed, as can be expected in model train applications.

U.S. Pat. No. 6,719,605 to Ichikawa (2004) discloses an electromagnet to generate a swinging motion on a swinging member, which is converted into wheel rotation through a ratchet mechanism. While avoiding the drawbacks of a DC motor based solution, this electro-magnet based solution was mechanically complicated.

U.S. Pat. No. 5,462,473 to K. Sheller (1995) discloses a leaky air bag that is built into collapsible stuffed toys (FIG. 2) such that when first compressed or folded, the stuffed toy will return to its relaxed posture slowly, mimicking life-like motions.

The above solutions suffer from one shortcoming or another—complex mechanisms, heavy current drain (especially when obstructed), or one-shot action that needs re-energizing (leaky air-bag).

OBJECT OF THE INVENTION

It is the object of the present invention to overcome or substantially ameliorated at least one of the above disadvantages and/or more generally to provide an improved low power article of motion. It is a further object of the present invention to provide low cost driving devices suitable for small toys that might be powered by miniature batteries and without resorting to complicated mechanisms.

SUMMARY OF THE INVENTION

According to the invention, there is provided an article of motion, comprising moving parts and an electronic timepiece movement, said parts being driven to move slowly and with low torque by the electronic timepiece movement.

Preferably, the timepiece movement would typically include a two-phase step motor.

In one embodiment, the article of motion is a toy vehicle, and said parts are wheels of the vehicle.

In another embodiment, the article of motion is a Ferris wheel driven to rotate slowly about an axis by the electronic timepiece movement.

In yet another embodiment, the article of motion is a figurine mounted to rotate upon a base within which the electronic timepiece is located.

The present invention typically employs a two-phase step motor, specifically the miniaturised genre as widely applied in timepieces (FIG. 1), to produce low-speed, low-torque motions suitable for use in classes of toys that need to move or articulate slowly.

The step motor axle rotates a fixed angle characteristic of its design when appropriate electrical stimulus is applied, and stay put indefinitely when no stimulus is received. The speed of a step motor depends solely on the external stimulus, thus simplifying the gear train needed when high-speed DC motor is used for low speed application.

The two-phase step motor typically directly drives the wheel of a toy car, or the limb or body part of a toy figurine, or the actuator in a model train railway is scenario. The amount of travel and the speed of execution are largely dependent on electronic stimulus applied. Where higher torque is needed, simple gear train can be installed between the step motor and the load.

Avoidance of high-ratio gear train lowers system energy loss during gear transmission, resulting in torque/battery-life combination optimally suited for slow-moving toys powered by small battery.

Two-phase step motors used in the timepiece industry output low-torque by nature. While a hindrance to other toy applications with heavier loads, the low torque adds to the safety of the toy, especially for infant or pre-school toys wherein the infant or young child is expected to obstruct the toy movements. Upon intervention the step motor will yield and stop its advance, while a DC motor would fight and try to continue its rotation, running down a battery quickly.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a parts-exploded perspective view of a prior art timepiece movement of a type including a two-phase step motor which might be adopted in the present invention;

FIG. 2 is a schematic perspective view of a first embodiment of an article of motion in accordance with the invention, comprising a rotating ballerina figure, a two-phase step motor, control circuitry and a drive transmission extending from the step motor to the ballerina figure;

FIG. 3 is a schematic top plan view of a second embodiment of an article of motion in accordance with the invention, taking the form of a toy motor car; and

FIG. 4 is a schematic side view of a third embodiment of an article of motion in accordance with the invention, which is a toy Ferris wheel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring initially to FIG. 2 of the drawings, there is shown a first article of motion embodying the invention in the form of a dancing ballerina for decoration, which comprises a ballerina FIG. 21 driven by a two-phase step motor 29 to turn on a base 39 resembling a stage. The step motor 29 has its output shaft 38 connected to an input gear 26 of an intermediate gear train 20. The output gear 27 of the gear train 20 has a shaft 22 onto which the ballerina FIG. 21 is mounted.

A child trying to stop a ballerina figure driven by a geared-down DC motor might suffer injury because of the heavy torque present, or the toy figure might be broken.

In a step motor based solution, the torque is much lower and neither the child nor the toy figure will be hurt in the event of jamming.

The step motor 29 receives control signals from circuitry 30 powered by battery or batteries 31. The gear train 20, the step motor 29, the circuitry 30 and the battery 31 are housed in the base 39 to prevent the child from making contact or tempering with these parts.

A variation on this theme is a dance figure that moves in varied tempo, including periods of suspended animation, thus better mimicking a real-life dance movement. Such variations can be conveniently implemented through delivering pre-programmed stimulus patterns to the step motor 29. This would otherwise require complicated mechanical mechanisms in a DC motor based solution.

Referring to FIG. 3, there is shown a second article of motion embodying the invention in the form of a toy car 10 for a child to play with. The step motor based toy car 10 will move slowly, but will provide a much longer play time than a DC motor based solution, assuming the same battery. Mounted on a chassis 11, a battery 12 powers the drive electronics circuit board 13 that delivers appropriate stimulus to step motor 14 that drives the rear wheel 15 directly or via a low-ratio gear box. When obstructed a DC motor toy car would draw a stall current typically larger than the normal operating current, and therefore run down the battery 12 quickly, or even burn out the motor winding. A step motor based toy car 10 will not draw excessive current when stalled.

Referring to FIG. 4, there is shown a third article of motion employing the invention in the form of a toy Ferris wheel 8 for decoration. An electronic driving circuit 16 provides electronic stimulus to a two-phase step motor 17 which drives the axis of the Ferris wheel 8 directly. It is conceivable that a child playing with such a toy might want to stop the Ferris wheel 8 abruptly to load or unload small toy FIG. 18 to or from the gondolas 19. The low torque of a step motor 17 will not counteract such an intervention especially if some suitable escapement mechanism is added between the step motor axis and the Ferris wheel 8 itself. Similarly constructed carousels and merry-go-rounds are easily conceived.

A model railway will also benefit from the present invention. Track-switches, signal lamps, locomotive and rolling stock can all be driven by the present invention without concern for obstruction-induced problems. A child can interrupt a locomotive safely, load a favourite figure before putting the locomotive back to the track, adding to playing enjoyment.

Advantages of the present invention include intrinsic low speed—diminished or remove requirement for gears, low torque—safe for infants and young children, intervention/obstruction-safe operation, no stall current upon obstruction, variable speed, including complete standstill—behaviour determined by external drive stimulus, low system cost, uses low cost step motor derived from proven timepiece technology.

Those skilled in the art will appreciate that the foregoing is presented by way of illustration only, and not as a limitation. Changes and modifications may be applied without deviating from the scope of the invention. 

1. An article of motion comprising moving parts and an electronic timepiece movement, the parts being driven to move slowly and with low torque by the electronic timepiece movement.
 2. The article of motion as claimed in claim 1, wherein the timepiece movement includes a two-phase stepping motor.
 3. The article of motion as claimed in claim 1, being a doll or figurine, wherein the parts are body parts of the doll or figurine.
 4. The article of motion as claimed in claim 1, being a toy vehicle, wherein the parts are wheels of the vehicle.
 5. The article of motion as claimed in claim 1, being a Ferris wheel driven to rotate slowly about an axis by the electronic timepiece movement.
 6. The article of motion as claimed claim 1, being a figurine mounted to rotate upon a base within which the electronic timepiece is located. 